Anatomical Changes during Rooting of Mangroves - Avicennia officinalis and Excoecaria agallocha.

Mangrove forests continue to disappear all over the world due to a number of reasons. This is the study made to screen the anatomical and biochemical changes during the rooting process. Two important mangrove species have been examined based on their salt relationship natures: Avicennia officinalis subsp. australasica (salt excreting plant) and Excoecaria agallocha L (salt accumulating plant). The plants were treated with different root promoting hormones like IBA, IAA and NAA at different concentrations for three minutes each. After 45 days of the growth period root growth and anatomical changes were observed. The roots originated from the deeper zone of the secondary xylem after several anatomical variations in the hormone treated plants. This is the first trial which may help to determine the mass propagation of these commercial and medicinally important mangroves.

Antioxidative response mechanisms in halophytes: their role in stress defence.

Normal growth and development of plants is greatly dependent on the capacity to overcome environmental stresses. Environmental stress conditions like high salinity, drought, high incident light and low or high temperature cause major crop losses worldwide. A common denominator in all these adverse conditions is the production of reactive oxygen species (ROS) within different cellular compartments of the plant cell. Plants have developed robust mechanisms including enzymatic or nonenzymatic scavenging pathways to counter the deleterious effects of ROS production. There are a number of general reviews on oxidative stress in plants and few on the role of ROS scavengers during stress conditions. Here we review the regulation of antioxidant enzymes during salt stress in halophytes, especially mangroves. We conclude that (i) antioxidant enzymes protect halophytes from deleterious ROS production during salt stress, and (ii) genetic information from mangroves and other halophytes would be helpful in defining the roles of individual isoforms. This information would be critical in using the appropriate genes for oxidative stress defence for genetic engineering of enhanced stress tolerance in crop systems.